The sync function does strange things on devices - rearranges bookmarks, incomplete sync, etc.
PhredE summed it up well already in another thread (http://support.mozilla.org/en-US/questions/937002#answer-403485) that was never satisfactorily resolved, yet closed. I just wanted it noted that more people are having the same problem. Syncs are incomplete, and bookmarks and folders get rearranged. Any time a change is made to a bookmark, such as moving it, the sync function takes several seconds to respond and ties up the interface while doing so.
Firefox isn't my life, I'm not going to spend a lot of time trying to troubleshoot and get the sync to work. Things should just work. I'm probably going to just take off the sync and use something else. I've already been playing with other browsers. This can't be that complicated.